Platelet-rich plasma in alopecia areata: intradermal injection versus topical application with transepidermal delivery via either fractional carbon dioxide laser or microneedling.

Introduction: Alopecia areata (AA) is a common cause of non-scarring alopecia with variable response to treatment. Platelet-rich plasma (PRP) stimulates proliferation and differentiation of stem cells in the hair-follicle bulge via multiple mechanisms. Although beneficial, pain during injection in addition to unequal delivery and coverage is a major drawback of intralesional PRP in alopecia, particularly for extensive lesions and in patients with a low pain threshold.